There are a variety of systems for monitoring and controlling manufacturing processes, inventory systems, emergency control systems, etc. Most automatic systems use remote sensors and controllers to monitor and automatically respond to system parameters to reach desired results. A number of control systems utilize computers to process sensor outputs, to model system responses, and to control actuators that implement process corrections within the system. Both the electric power generation and metallurgical processing industries successfully control production processes by implementing computer control systems in individual plants.
For example, many environmental and safety systems require real-time monitoring. Heating, ventilation, and air-conditioning systems (HVAC), fire reporting and suppression systems, alarm systems, and access control systems utilize real-time monitoring and often require immediate feedback and control.
A problem with expanding the use of control system technology is the cost of the sensor/actuator infrastructure required to monitor and control such systems. The typical approach to implementing control system technology includes installing a local network of hard-wired sensor(s)/actuator(s) and a local controller. There are expenses associated with developing and installing the appropriate sensor(s)/actuator(s) and connecting functional sensor(s)/actuator(s) with the local controller. Another prohibitive cost of control systems is the installation and operational expenses associated with the local controller.
FIG. 1 sets forth a block diagram illustrating certain fundamental components of a prior art control system 100. More particularly, a prior art control system 100 includes a plurality of sensor/actuators 111, 112, 113, 114, 115, 116 and 117 electrically and physically coupled to a local controller 110. In a manner well known in the art of control systems, local controller 110 provides power, formats and applies data signals from each of the sensors to predetermined process control functions, and returns control signals as appropriate to the system actuators. Often, prior art control systems are further integrated via the public switched telephone network (PSTN) 120 to a central controller 130. Central controller 130 can also serve as a technician monitoring station and/or forward alarm conditions via PSTN 120 to appropriate officials.
Prior art control systems similar to that of FIG. 1 require the development and installation of an application-specific local system controller. In addition, each local system requires the direct coupling of electrical conductors to each sensor and actuator to the local system controller. Such prior art control systems are typically augmented with a central controller 130 that may be networked to the local controller 110 via PSTN 120. As a result, prior art control systems often are susceptible to a single point of failure if local controller 110 goes out of service. Also, appropriately wiring an existing industrial plant can be a dangerous and expensive proposition.
Accordingly, there is a need for monitoring and control systems that overcome the shortcomings of the prior art.